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Picture Climate: Why Are Buckets Important to Climate Science?

Wooden bucket used to measure sea surface temperatures during World War II. Credit: The Mariners’ Museum

This may look like an ordinary bucket, but less than a century ago, scientists and sailors used buckets just like this one to measure sea surface temperatures. Sea surface temperature readings are taken at the top layer of the ocean. Scientists use these temperatures for everything from monitoring ecosystems to predicting El Niño and La Niña events.

So, how were buckets used to measure sea surface temperatures? Sailors would lower these buckets over the sides of their ships and drag them through the water until the buckets were full. Next, the sailors would hoist the buckets back up to the ship deck, where they inserted a mercury thermometer into the water and allowed it to sit for generally about three minutes. They then recorded these temperatures in the ship’s logbook.

As you can probably imagine, these measurements weren’t always the most accurate. The bucket method for measuring sea surface temperatures often led to cooler readings. This was due in part to evaporation that occurred as the bucket was hauled back onto the ship and while the thermometer was equilibrating. And, evaporation is a cooling process, which means that as it converts water from liquid to vapor, it cools the surrounding environment.

A moored buoy, one that is anchored to the ocean floor, is deployed over the side of the Delaware II. Credit: NOAA

Fortunately, as time progressed so did technology, allowing scientists to develop more accurate methods for measuring sea surface temperatures. Today, buoys across the oceans automatically report measurements from their sensors. These measurements are beamed to satellites for automated and immediate data distribution. The National Data Buoy Center maintains a large network of coastal buoys in U.S. waters. These buoys range in size from around 5 feet to nearly 40 feet in diameter—nearly seven times the height of the average American male! However, buoys aren’t just found in U.S. coastal waters. The National Data Buoy Center also collaborates with several international agencies to monitor sea surface temperatures across the globe.

Sea surface temperatures can affect many things from the formation of tropical cyclones to the amount of precipitation and where it falls. Perhaps most importantly, these temperatures affect the behavior of the Earth’s atmosphere above them, making monitoring them extremely important. Collaborating with the international community, NCDC continues to aid in the effort to monitor and archive sea surface temperatures from around the world to provide scientists, constituents, and the public with the best available information to anticipate their effects on the environment and the climate.